Transparent electroconductive films including a substrate of a transparent plastic film and a transparent electroconductive thin film laminated on the substrate are used in a variety of applications utilizing their electrical conductivity including flat panels such as liquid crystal displays, touch panels for smartphones, car navigation systems and digital cameras, and electromagnetic shielding films for shielding electromagnetic waves from display screens of liquid crystal displays and plasma displays or electromagnetic waves from cellular phones.
Touch panels are categorized, according to their position detection method, into several types including optical type, ultrasonic wave type, electromagnetic induction type, capacitance type and resistance film type. A resistance film type touch panel has a structure in which a transparent electroconductive film and a glass with a transparent conductive layer (indium tin oxide, which is hereinafter abbreviated as “ITO”) laminated thereon are opposed to each other with dot spacers therebetween. When the transparent electroconductive film is pressed, the transparent conductive layer (ITO) on the opposing glass substrate and a transparent conductive layer (ITO) of the transparent electroconductive film are electrically connected at a point where there is no dot spacer so that the position of touch can be determined. Thus, the problem is that the touch panel reaches the end of its service life when the strength of the dot spacers or the ITO decreases. On the other hand, a capacitance type touch panel has a transparent conductive layer patterned on a substrate. When the touch panel is touched with a finger or the like, the capacitance of the finger is detected, causing a change in the resistance value between the touched point and the patterned transparent conductive layer. This allows accurate detection of two-dimensional positional information. Because of their structure, the capacitance type touch panels are characterized by having no movable parts, and have high reliability, a long service life, and excellent optical characteristics such as transparency.
As described above, in some touch panels, the transparent conductive layer of the transparent electroconductive film is provided with a predetermined pattern so that the input position can be detected. However, when patterned portions (portions having a transparent conductive layer) and non-patterned portions (pattern opening portions having no transparent conductive layer) having a clear difference in optical characteristics are formed by the patterning, the panels may have poor appearance as display elements. In particular, in the case of capacitance type touch panels, because the transparent conductive layer is formed on the front surface of the display, a transparent conductive layer having a good appearance even when patterned is required.
In addition, because the electromagnetic waves generated in liquid crystal displays may cause malfunction of touch panels, a transparent electroconductive film is inserted between the touch panel and the liquid crystal display of capacitance type touch panels to provide a function against electromagnetic interference (EMI). Such a transparent electroconductive film must have few or no other factors that may affect the appearance of the panels as display elements (such as the formation of interference fringes and a decrease in light transmittance).
For example, Patent Literature 1 discloses a transparent electroconductive laminate including a film substrate and an electroconductive thin film provided on the substrate. The transparent electroconductive laminate is superior not only in transparency and scratch resistance of the electroconductive thin film but also in flex resistance (refer to paragraph 0005 of Patent Literature 1).